What is the cause of the overheating of the mechanical seal of the DG boiler feed pump?
DG type boiler feed water pump device, the mechanical seal of the mobile equipment accounts for about 80%-85% of the total dynamic seal. In the mechanical pump failure, the mechanical seal failure accounts for about half of the total maintenance workload. It can be seen the position occupied by the mechanical seal in the maintenance of the pump. Since the media conveyed by the pumps are very different and the process conditions are different, it is important to understand these conditions for the selection and maintenance of the mechanical seal.
Boiler feed pump
DG type multi-stage boiler feed water pump mechanical seals will fail due to overheating, which is thermal damage failure. Common thermal damage failures include end face thermal deformation, thermal cracking, blister scars, carbonization, loss of elastic components, rubber parts Aging, deformation, cracking, etc. Many small hot spots and isolated discoloration areas are sometimes found on the sealing end surface, which indicates that the seal is locally deformed and distorted under the influence of high pressure and heat, and sometimes symmetrical and discontinuous bright bands are found on the sealing end surface. This is mainly It is because of irregular cooling that causes local thermal deformation of the end face. Why is the mechanical seal of the boiler feed water pump thermally damaged? The following editor will analyze it for you:
1. High leakage in high temperature environment of mechanical seal
In the mechanical seal under high temperature environment, pits and scars are often found on the surface of the graphite ring. This is because when the resin-impregnated graphite ring exceeds its allowable temperature, the resin will be carbonized and decomposed to form hard particles and precipitate volatiles, forming scars, thereby greatly increasing friction and causing high leakage of surface damage.
The environment may reduce the elasticity of the elastic element, thereby making the closing force of the sealing end face insufficient and causing serious leakage of the sealing end face. The high temperature loss of metal bellows is a common and typical failure mode of this type of mechanical seal. The effective way to avoid this is to select a reasonable corrugated pipe material and conduct proper heat treatment.
2. High temperature is an important reason for the aging of mechanical seal rubber seals
High temperature is an important reason for the aging, cracking and deformation of rubber seals. Rubber aging is manifested by the hardening of the rubber, the decrease in strength and elasticity, and cracking in severe cases, resulting in loss of sealing performance. Overheating can also decompose the rubber components and even carbonize. In high-temperature fluids, the rubber ring may continue to vulcanize, and the ui will eventually lose its elasticity and leak. The deformation of rafter seals is usually more serious than other materials. The sealing ring will become the same shape as the groove when it is exposed to high temperature for a long time. When the temperature remains the same, it can also play a sealing role; but when the temperature drops, the sealing ring will quickly shrink, forming a leakage channel and causing leakage. Therefore, attention should be paid to the use temperature of various glue types, and long-term use at extreme temperatures should be avoided.
3. Failure of mechanical seals of boiler feed water pump due to overheating
Failure caused by overheating is thermal damage failure. Common thermal damage failures include end face thermal deformation, thermal cracking, blistering, carbonization, elastic element loss, and rubber aging, deformation, and cracking. The thermal deformation of the sealing end face of the boiler feed water pump includes local thermal deformation and overall thermal deformation. Many small hot spots and isolated discoloration areas are sometimes found on the sealing end surface, which indicates that the seal is locally deformed and distorted under the influence of high pressure and heat; sometimes it is found that there are symmetrical and discontinuous bright bands on the sealing end surface. It is because of irregular cooling that causes local thermal deformation of the end face. Sometimes it is found that the seal end face wears very seriously on the inside, the larger the radius, the shallower the contact marks, until they are indistinguishable. The inner edge of the sealing ring may show chipping and edge jumping. When the shaft rotates, the seal continues to leak, but does not leak when the shaft is stationary. This is because when the seal is in operation, the outer side is cooled sufficiently, and the inner side frictional heat is serious, so the inner thermal deformation is greater than the outer thermal deformation, forming an inner contact type (positive cone angle) end surface caused by thermal deformation.
4, the brittle material seal ring dry friction, cooling suddenly interrupted due to thermal damage failure
Sealing rings of brittle materials such as cemented carbide, engineering ceramics, carbon graphite, etc., sometimes radial cracks appear on the end faces, so that the leakage of the sealing surface increases rapidly, and the mating parts wear sharply. This is mostly due to the dry friction of the sealing surface and the sudden interruption of cooling. A kind of thermal damage failure caused by the rapid accumulation of friction heat on the end face and other reasons.
